1. Field of the Invention
The present invention relates to a substrate surface potential measuring apparatus and a plasma processing apparatus, and more particularly, to a substrate surface potential measuring apparatus capable of measuring the surface potential of various kinds of substrates in a plasma processing apparatus and a plasma processing apparatus capable of accurately controlling ion energy.
2. Description of the Related Art
Plasma processing apparatus are widely used for forming various kinds of thin films and etching in a semiconductor production process. In order to positively utilize ions incident on a substrate and achieve processing of high reproducibility by using such processing apparatuses, it is very important to precisely measure and control the energy of the ions.
Ion energy is expressed as a difference between the plasma potential and the surface potential of a substrate. Although the plasma potential can be measured by using, for example, a Langmuir probe, a method of accurately and easily measuring the surface potential of the substrate has not been established yet. Therefore, various processes are performed by approximating the ion energy by the plasma potential and controlling the plasma potential.
However, since the surface potential of the substrate varies according to the material, thickness, set conditions and the like thereof, the ion energy cannot be accurately measured or determined using such method. As a result, for example, the quality of deposited films varies batch by batch, and this variation leads to a low yield of TFT substrates for liquid crystal displays.